I've been adding some Huben cultivars to my garden because I, too, am looking for border plants that can rebloom in my Northern climate. I kind of differentiate disconnected rebloom from instant rebloom. So by rebloom, I mean it blooms for a while, shuts down for a while, and comes back, often when temperatures cool off a bit.
Early and Often was my first Huben purchase. Last year it bloomed June 15 to July 1, July 24 to August 18, and September 6 to September 18, for a total of 56 days (8 weeks) worth of blooms. Three reblooms is pretty rare for my Zone 5A location. So I'm pretty happy with it, and it's still a pretty small clump and will improve. In my garden, that puts this in a class with Happy Returns and not quite Stella de Oro, if you are familiar with those.
Early and Often
Not mentioned, I added White and Nerdy which hasn't rebloomed for me, yet, in two summers. I'm adding Magenta Kisses and But I Repeat Myself this spring, so check back again in a couple years.